It has not been a vintage Wimbledon, but after a fortnight of unexpectedly benign weather and predictably anti-climactic British performances, we have at least ended up with the men's final - sorry, Andy - that every tennis fan wanted. This afternoon, weather permitting, Rafael Nadal and his comic-book muscles will take on Roger Federer and his £260 five-button, herringbone cardigan in front of 14,000 people on Centre Court and, the BBC estimates, around 8 million at home. It is the latest and potentially most dramatic instalment of what has become the most satisfying rivalry in modern sport.

Almost everything about the two is different. Federer, the five-time All England champion, is the Lord of the Lawn, unbeaten in 65 matches on grass. The epitome of Swiss elegance, he does not seem to possess sweat glands and dresses, without apparent irony, like Sebastian Flyte from Brideshead Revisited. Aged 26, winner of 12 grand slams, he can make watching tennis a spiritual experience and is within a whisper of being, without dispute, the greatest player the game has ever seen.

On the other side of the net, for the third year running at Wimbledon, is Nadal, the 22-year-old Colossus of Clay from Mallorca. An embodiment of Spanish machismo, he is a southpaw with a front-on, windscreen-wiper forehand that delivers 3,200rpm of topspin - 20 per cent more than Federer. A devotee of sleeveless shirts and Capri trousers over apparently uncomfortable underwear, he has not, unlike his opponent, been seen on the front row of a fashion show with US Vogue editor Anna Wintour. The world number two, Nadal is unbeaten in 23 matches, including a comprehensive tanning of today's opponent in the final of the French Open last month.

Something has to give. Either Federer wins his sixth consecutive title, and breaks Björn Borg's record in the process, or Nadal takes his first Wimbledon and becomes, whatever the rankings say, the best player in the world. 'The bottom line is who wins the slams,' says BBC commentator Andrew Castle. 'If Nadal wins - and the professional sporting money seems to think he will - then for most people he will be the top dog.'

Federer says he has no problems with the shifting odds, but any man who wears a belt to play tennis is unlikely to take kindly to being beaten by an upstart dressed as a pirate.

'You can always say what you like,' the Swiss said, after dispatching Marat Safin in straight sets in Friday's semi-final (he is yet to drop a set in this year's tournament). 'I was a little surprised with how intense it was, but it was because Rafa played so well in Paris, and then winning Queen's. But don't write me off too quickly because this is my part of the season now: Wimbledon, the Olympic Games, the US Open.'

What is almost as unexpected is the fact that Nadal, having easily beaten the hapless Rainer Schüttler in his semi, goes into today's final as perhaps the marginal crowd favourite. Andre Agassi was one of the first to point out that Federer's sublime skills would not always endear him to the masses ('Roger makes it look too easy,' he said in 2006. 'It's easier to identify with Nadal.')

Wimbledon, against expectations, seems to have taken to the Spaniard. When he played Andy Murray on Wednesday, it was impossible not to notice that Nadal received the louder cheers when he entered Centre Court. 'I felt really appreciated when I stepped out on court,' he wrote on his blog the next day. 'The round of applause was extraordinary considering I was playing against their player.'

We have learned much about Nadal in the last two weeks, although mostly from his online Q & As, rather than his increasingly assured performances on grass. Just a reminder; he eats pasta with prawns and mushrooms every night, he is afraid of the dentist and ghost stories, and he goes to bed in just his underpants. One cannot help but wonder how Federer would have answered that last question. Presumably, silk pyjamas and a cravat.

Nadal's street-fighting style certainly appeals to younger supporters and to women who have not read in the Daily Mail about Xisca, his 'secret' girlfriend of three years.

On Facebook, he has a general fan group with nearly 60,000 members - 'I love Rafael Nadal' has 5,763 affiliates and 'Nadal owns Roger Federer' 894. The 'Federer is betterer' group has 2,058 members and 'Rafa Nadal isn't sexy, isn't entertaining and is owned by Federer' has 417. However, both players are topped in this respect by a fan site for the world number three player - 'F**k Federer and Nadal, Djokovic is best' has been joined by 6,567 Facebookers.

Even in retail, the rivals, both fitted out by Nike, have their devoted demographic. 'It's quite a mix of customers who want to buy Federer's cardigan,' says the manager of Nike Tennis's pop-up store in Wimbledon. 'Some older, more traditional fans who like the tailored style, some sports memorabilia collectors, because there are only 230 available. But it's quite distinct from the crowd who buy Nadal's outfits, which tends to be teenagers, because they like the way Rafa wears it.'

The only thing that the Federer-Nadal rivalry lacks is genuine antipathy between them. Federer is scrupulously complimentary about Nadal and even gave him a lift on his private jet when the Spaniard was stuck between tournaments. Nadal, in turn, is positively reverential. When he brutalised the world number one in Paris 6-1, 6-3, 6-0 - one of the defining performances of recent years - he barely celebrated in case it came across as gloating. Even last week, asked about his chances for Wimbledon, he said: 'I think Roger is a more elegant player than me. I think he has more options on court. He can do everything.'

Today's match is impossible to call. Nadal is playing better than he ever has on grass, but, arguably, so is Federer. Borg thinks Nadal has the edge, but most commentators, says Castle, have a feeling that Federer is holding just enough back. Both players are fit, match fresh and at the peak of their powers. It should be quite something. Only the weather can ruin it now.